In recent years, a mobile phone in which a camera module is incorporated has become the model which accounts for the majority of the models of mobiles phone used. Such camera modules are required to achieve higher levels of reduction in size and weight as compared with digital cameras, since the camera modules have to be contained within a mobile phone.
Among the camera modules, a type whose automatic focus (AF) function is realized by means of an actuator for driving a lens is in increasing use. The actuator can be classified into various types, for example, a type which uses a stepping motor, a type which uses a piezoelectric element, and a type which uses a VCM (Voice Coil Motor). These types of actuators are already on the market. Similarly, with regard to support means for supporting a lens and movably guiding the lens in a predetermined direction, various methods such as a method of causing a lens to slide along a guide shaft, a method of using the rolling of a ball, and the like have been proposed, although the mainstream method is to use a spring. There has also been proposed a method which uses means that serves both as an actuator and as support means, the means being a shape-memory-alloy wire, for example.
For example, Patent Literature 1 discloses an arrangement which serves both as an actuator and as support means. Specifically, Patent Literature 1 discloses a camera module which is constituted by (i) an actuator which includes (a) a lens barrel containing an optical element and (b) a lens carrier containing the lens barrel, (ii) a solid-state image sensing device, (iii) a substrate, and (iv) the like. The camera module of Patent Literature 1 employs, as a member for holding the optical element, a double structure constituted by the lens barrel and the lens carrier. Accordingly, the camera module is increased in size due to a thickness of the lens barrel.
In view of this, in order to reduce a size of the camera module, Patent Literature 2 proposes, as a structure that can avoid the double structure, a structure which uses no lens barrel. According to an arrangement disclosed in Patent Literature 2, after an image pickup section and a bottom section of an actuator are assembled, lenses are provided on top of the image pickup section and the bottom section assembled, and then adjustment of a distance between the lenses and fixation of the lenses to each other via an adhesive are carried out simultaneously. Subsequently, other members of the actuator are assembled. However, the structure disclosed in Patent Literature 2 has the following problems. According to the structure disclosed in Patent Literature 2, the lens unit is incorporated while the actuator is being assembled. This may result in a stain or a scratch on a surface of a lens during a step of incorporating the actuator. Further, according to Patent Literature 2, the adjustment of the distance between the lenses of the lens unit and the fixation of the lenses to each other via the adhesive are carried out while the actuator is being assembled. Accordingly, evaluation of the lenses in terms of optical performance is carried out after the actuator is assembled. In this case, a defect of the lenses results in a defect of a whole product including the actuator, so that a cost of defective work is increased. This may cause (i) an increase in defective-product ratio among completed actuators and (ii) a decrease in production efficiency, accordingly.